1. Field of the Invention
The present invention relates to a method for forgery recognition in fingerprint recognition by using a texture classification of gray scale differential images and particularly to a method for forgery recognition in fingerprint recognition based on a image sequence. In particular, the present invention relates to a dynamic software-based method for forgery recognition.
2. Description of Related Art
Fingerprint recognition is a reliable and widespread technique for personal identification. Several methods for the recognition of fingerprints are known in the related art, at first, the simple image recognition that capture an image of a finger being placed and compare it with stored images to identify a person.
The drawback of those methods is that they are very easy to deceive, for example by placing a silicone cast of a fingertip or something similar. Further, the large storage need for the comparison images (“templates”) being used as well as the large computing effort are disadvantageous. The disadvantage of easy deceit also exists in minutien-based methods.
For the solution of these problems the related art has suggested to extract features from the fingerprints and to perform the recognition based on these features. Known biometric methods for personal recognition can for example be implemented in automated systems. Such systems process the input data comprising the biometric features and extract characteristic features that can then be associated with a person.
However, for a reliable personal association it has to be made sure that no manipulation is possible on the signal path between the object to be measured and the image capturing means.
In the recognition of fingerprints by an automatic system for fingerprint recognition methods are therefore necessary that only pass on images generated from real fingers to the processing means and eventually refuse images from imitations.
Approaches for solving these problems known in the related art will be discussed briefly below, wherein a distinction is made between hardware-based solutions and software-based solutions.
A first solution is to supplement the sensor by which the fingerprint is to be captured with integrated or external hardware components. Such known solutions capture, for example, an impedance of the placed fingers, as it is described in more detail in U.S. Pat. No. 5,953,331. Other technical realisations of hardware-based forgery recognition comprise moisture measurement, pulse measurement and pressure measurement.
Apart from the hardware-based solutions, solutions are known where the data for forgery recognition are evaluated via software. In the software-based forgery recognition there is made a distinction between static and dynamic methods.
In the static methods only one image is evaluated, usually the one that is also used for recognition. Static software-based forgery recognition method base for example on the evaluation of fingerprint images that exist as bitmap with gray scales. Other software-based static methods evaluate the sebaceous glands visible in the image.
In the dynamic methods a sequence of consecutive images of the sensor describing the process of placing the finger is used. A dynamic forgery recognition increases the recognition and forgery security of biometric fingerprint systems, where additionally, for example, a movement of the person, a pressure with which the finger is placed, or sweat on the finger are taken into account in the recognition. Other dynamic methods take the respective information for forgery recognition from sequences of finger print images.
The above-described dynamic software-based solution for forgery recognition, where respective information is extracted from sequences of finger print images for forgery recognition, is based on the large area deformation of the skin and therefore the fingerprint, which is known as “macro elasticity”. The disadvantage of using the macro elasticity is that visible differences between original fingers and forgeries in general can only be recognised when the finger or the forgery are being placed with considerable pressure.